The prior art additive consisting of or comprising zinc octoate (ZnOctoate) is known to scavenge hydrogen sulphide (H2S) in asphalt/bitumen/crude oil/hydrocarbons.
The U.S. Pat. No. 5,000,835 discloses use of zinc octoate, zinc naphthenate as H2S scavenging additive in asphalt.
The U.S. Pat. No. 8,246,813 B2 discloses use of zinc octoate as H2S scavenging additive in crude oil.
The US patent publication no. US 2015/0025258 A1 discloses a method for preparing zinc carboxylate oxo complex composition and discloses use of zinc octoate as H2S scavenging additive in hydrocarbons.
The U.S. Pat. No. 9,278,307 B2 discloses use of a combination of zinc octoate and dibutylamine formaldehyde reaction product as H2S scavenging additives in crude oil.
The US publication no. US 2008/039344 A1 discloses use of a zinc compound, such as zinc citrate as chelating agent to form a chelate between the metal (Cu or Zn) and a base being monoethanol amine (MEA).
The US publication no. US 2014/190870 A1 discloses use of a composition comprising at least one transition metal and at least one water-soluble aldehyde or water-soluble aldehyde precursor.
The US publication no. US 2005/145137 A1 discloses a composition of zinc with ethanolamine and mercaptobenzothiazole (MBT).
However, none of the prior art document discloses or teaches how to reduce the amount of the additive 1 of the present invention, that is, how to overcome the problem of using higher amount of the prior art additive 1 to scavenge the H2S so as to have economical composition for scavenging hydrogen sulfide in the medium.
The US patent publication no. US 2011/0160355 discloses use of polyphosphoric acid (PPA) (the additive 2) as H2S scavenging additives, but without combining it with ZnOctoate.
However, the industry further treats the medium treated with the additive 1 (for example, with ZnOctoate) with the additive 2 (i.e. with polyphosphoric acid (PPA)). However, the Inventor of the present invention has found that the said further treatment with the additive 2 (i.e. with polyphosphoric acid (PPA)) of the medium treated with the additive 1 (for example, with ZnOctoate) causes re-release of the scavenged H2S back into the medium, and thereby, reduces the hydrogen sulfide scavenging efficiency of the additive 1.
For example, when just 25 ppm, 50 ppm, and 75 ppm of the additive 1 was added to the medium containing 2000 ppm of H2S, the % efficiency of the additive 1 to scavenge the H2S in the medium was, respectively found to be 50%, 92.5%, and 100% (respectively referred to as ‘treated medium 1A’, ‘treated medium 1B’, and ‘treated medium 1C’)—Re Expt. Nos. 1, 3 and 5 of Table 1.
However, the Inventor of the present invention has found that when the treated medium 1A, the treated medium 1B, and the treated medium 1C were separately further treated with just 1% by weight of the additive 2, then the efficiency of the additive 1 was, respectively found to substantially reduce from 50% to 30%, from 92.5% to 57.5%, and from 100% to 65%, respectively, in case of the treated medium 1A, the treated medium 1B and the treated medium 1C (Re Expt. Nos. 2, 4, and 6 of Table 1).
Such reduction in the hydrogen sulfide scavenging efficiency of the additive 1 on addition of the additive 2 in the medium treated with the additive 1 may be attributed to the reasons of re-release of the scavenged H2S back into the medium on addition of the additive 2.
These experiments have shown that addition of the additive 2 substantially reduces the hydrogen sulfide scavenging efficiency of the additive 1, and hence, the additive 2 has a negative effect on the hydrogen sulfide scavenging efficiency of the additive 1.
Therefore, the additive 2 (for example, PPA), which is not only expensive, but also causes re-release of hydrogen sulfide from the medium treated with the additive 1 (for example, with ZnOctoate), and hence, the additive 2 has a negative effect on the hydrogen sulfide scavenging efficiency of the additive 1.
However, the asphalt/bitumen such treated with the additive 1 is modified prior to use in roads/pavements/highways/airstrips etc. The additive 2 (for example, PPA) is the primary level of modifying agent used to improve various properties of the asphalt/bitumen. When the additive 2, i.e. PPA is thus added, it causes release of the H2S from the asphalt/bitumen treated with the additive 1, and hence, the additive 2 has a negative effect on the H2S scavenging efficiency of the additive 1.
The industry has, therefore, desired either to reduce the amount of the additive 2, that is, PPA, or to eliminate it totally from the composition, so that its negative effect on the hydrogen sulfide scavenging efficiency of the additive 1 (i.e. ZnOctoate) may be reduced or eliminated.
The industry is, therefore, looking for an improved additive composition which is capable of improving H2S scavenging efficiency of the additive 1.
The industry is, therefore, also looking for an improved additive composition which is capable of improving H2S scavenging efficiency of the additive 1 even in presence of the additive 2, that is, capable of eliminating or at least reducing the negative effect of the additive 2.
Therefore, there is a need to have a solution to the above-discussed industrial problems.
Particularly, there is a need to have:
(I) An improved hydrogen sulfide (H2S) scavenging additive composition which is capable of improving H2S scavenging efficiency of the additive 1; and
(II) An improved hydrogen sulfide (H2S) scavenging additive composition which is capable of improving H2S scavenging efficiency of the additive 1 even in presence of the additive 2, that is, at least capable of reducing the negative effect of the additive 2; and
(III) A method of scavenging hydrogen sulphide in the medium by employing the improved hydrogen sulfide (H2S) scavenging additive compositions of the present invention; and
(IV) A method of using the improved hydrogen sulfide (H2S) scavenging additive compositions of the present invention for scavenging the hydrogen sulphide in the medium.